society > travel > travel by water > vessel, ship, or boat > equipment of vessel > masts, rigging, or sails > rigging > [noun] > running rigging > chain securing jib-boom
crupper-chain1882
1882 G. S. NaresSeamanship (ed. 6) 13Crupper chain, a chain passed round the bowsprit and the heel of jib-boom to secure the latter down in its saddle.